Custom-Shaped Freestanding Conducting Oxide Membranes on Demand

Creating freestanding oxide membranes with shape control opens the possibility to study a highly desirable range of feature sizes for future experiments and devices. One of the main challenges in patterning freestanding membranes is the tedious process required to synthesize the films, release and transfer them, and then shape them into a desired design. The question is whether we can achieve the desired shape in a single step, thereby eliminating numerous intermediate fabrication stages and allow the study of devices where the twist angle with respect to the new substrate can be varied systematically. Here, we present a simple and straightforward procedure to produce patterned freestanding membranes, which requires minimal laborious and time-consuming fabrication steps. Deposition of thin films is carried through shadow masks, which are placed between the material source (in this case, a PLD target) and the sacrificial layer on which the material is deposited. By doing this, a thin layer of material is deposited and structured simultaneously. The patterned structure is then transferred on a substrate of choice, in this case on SiO2. The resolution of a shadow mask depends on two key parameters: the size of its features and the thickness of its mask. The relationship between these parameters is called the aspect ratio. The highest resolution is achieved when the aspect ratio is one. At this ratio, the influence of the mask's sidewalls on the dimensions of the deposited material is minimized, allowing for more precise patterning. In the current work we have used STO-based conducting oxide as an example. The membranes were grown in a Hall-bar shape and then transferred. Transport measurements were performed to study both the electric and magnetic properties.